The FDA today revoked its 2008 approval of the drug Avastin to treat breast cancer, concluding that the drug does little to help women with breast cancer while putting them at risk for potentially life-threatening side effects. Avastin will remain on the market (and so be potentially available to women with breast cancer) because it has also been approved to treat other types of cancer.

FDA recognizes how hard it is for patients and their families to cope with metastatic breast cancer and how great a need there is for more effective treatments. But patients must have confidence that the drugs they take are both safe and effective for their intended use. After reviewing the available studies it is clear that women who take Avastin for metastatic breast cancer risk potentially life-threatening side effects without proof that the use of Avastin will provide a benefit, in terms of delay in tumor growth, that would justify those risks. Nor is there evidence that use of Avastin will either help them live longer or improve their quality of life.

Why does this happen?

Every new drug is tested in a series of clinical trials. Small phase I trials evaluate a drug’s safety, determine a safe dosage range, and identify side effects. Somewhat larger phase II trials test the drug’s effectiveness and further check its safety. In phase III trials, the drug is given to large, carefully defined groups of people to confirm its effectiveness, monitor side effects, compare it to commonly used treatments, and gather other information on side effects and safety. Phase III trials are the ones the FDA uses to determine if a new drug should be approved.

Avastin went through this process. In the two phase III trials on which the FDA based its approval, the drug was tested in just under 1,200 women. As a condition of approval, the FDA required Genentech, the company that made the drug, to carry out additional trials. These weren’t so positive.

Another important issue is that real life is messier and more diverse than clinical trials. Once a drug is approved, anyone with the specified condition can take it. The folks taking the drug may be older than those allowed into the phase III clinical trials, have other medicals conditions, be taking other medications, or have other important differences from the clinical trial populations. And that often translates into less effectiveness and more side effects and complications than seen in the trials. Although the FDA often requires companies to study how the drug performs once it is being used in clinical practice, a report by the Department of Health and Human Service’s Office of Inspector General found that the FDA often doesn’t follow up to make sure these studies are undertaken.

We’re all individuals

The FDA bases its decisions on data collected from large, diverse groups. While the decision that Avastin isn’t effective against breast cancer applies to most women, it is possible that some women may benefit from the drug. But at least for now, it’s impossible to know in advance who might benefit from the drug.

The Avastin story underscores the idea that it takes a while for a drug’s full effects to be revealed. In other words, when it comes medications, new isn’t necessarily better.